Body odor, sweating and bacteria involved

Information 15/09/17.


skin secretions

Sweating and body odor linked to it, they are common events for most people. Excessive sweating can occur when exercise is performed when there are high ambient temperatures, or when you are nervous, anxious or stressful situations.

Sweating occurs through two types of sweat glands, eccrine glands and apocrine glands. These two types of glands produce two very different types of sweat. Both types of sweat are themselves toilets.

Eccrine glands are present in almost all the body surface and open directly to the skin surface. Apocrine glands, unlike the previous ones , are abundant in hair follicles areas, as with armpits and English, and drain secretion into the top of the hair follicles, just before those open to the skin surface .

When body temperature rises, eccrine glands secrete liquid to the skin surface, so that the body cools as the secreted liquid evaporates. This liquid is mainly composed of water and salt.

Apocrine glands, however, produced a milky liquid, also colorless and odorless until it comes into contact with the bacteria present on the skin, at which time results in a bad smell.

This is the reason why odor attributed to bacterial degradation of precursors present in sweat. These bacteria would be that metabolize various products secreted by the apocrine glands in the neck of the hair follicle, generate volatile odor causing products.

Several factors such as age, sex, genetic factors, environmental factors (climate or stressful situation), personal hygiene, or the use of cosmetics, among others, can contribute to body odor, as these factors change, in one way or another , amount of sweating, their properties or types of bacteria present on the skin.

Bacteria involved in odor

The skin consists of many ecological niches, each with a specific bacterial community. There are very dry areas such as the forearm, the trunk and legs with a bacterial density of about 10 2 bacteria / cm 2, while in the umbilical region, and interdigital spaces feet density is of 10 7 bacteria / cm 2 .

Have been identified by culture, several groups of bacteria as the most involved. Traditionally bacteria have been investigated aerobic and therefore has always spoken of Corynebacterium spp. (C. striatum, C.jeikeium), Staphylococcus spp. (S. epidermidis, S. haemolyticus), and Micrococcus spp.

When cultures were performed anaerobically found Propionibacterium spp. (P. acnes), and some other anaerobes (Anaerococcus spp.).

Currently, studies are being made with massive sequencing, and are being found in bacteria belonging to 19 different bacterial groups.

Cutaneous microbiota is usually stable, thanks to the lipid components, desquamation of the skin stratum corneum, and skin temperature. This stable microbiota confers resistance vs. host penetration of microorganisms that could cause infections.

Studies have been conducted to compare the microbial flora in different individuals. Some studies found differences between men and women. Coryneform bacteria (Corynebacterium spp.) Would be more prevalent among males, and contribute to more pronounced odor thereof. The high nutritional content and moisture favor the development of coryneform bacteria, and inhibit the growth of gram - positive cocci (Staphylococcus spp. And Micrococcus spp.). Furthermore, apocrine glands of males are larger and have greater activity.

Other studies have investigated the skin flora according to some underarm hygiene practices, such as shaving, the use of certain cosmetics and deodorants. The differences justify the different profile of the smell of one individual to another, because they change the volumes of fluids secreted by these glands, change the profile of the skin microbiota or their metabolic activity. Some cosmetics have components that can be used as nutrients for bacteria, as with cosmetics containing glycerin, amino acids, hydrolyzed collagen, or antimicrobial substances which may favor the presence of resistant bacteria.

Woven clothing and skin flora

Clothing fabrics coming into intimate contact with skin organisms and the environment. These fabrics create a warm and moist frequency on the skin, which promotes the growth of bacteria on the skin and clothing fabrics own environment.

The development of these bacteria, and produce odors, sometimes unpleasant, can lead to discoloration, tissue damage, physical irritation, allergic diseases, or skin infections.

Transfer of microorganisms from the skin tissue fibers occurs in several stages: adhesion, growth and fiber damage. The growth of bacteria in the tissues of clothing is due to secretions of the apocrine sweat glands and products containing the skin desquamation, existing natural particles in the fibers of the tissues, and sometimes the fibers themselves .

We have studied the relationship between the type of fabric of the clothing and the smell generated. In principle it is conceivable that natural fibers may be more easily affected by microbiota due to natural nutrients in them. Thus, the cellulose fibers are degraded by certain bacteria or fungi that possess cellulolytic enzymes.

Synthetic fibers which typically have in its constitution phthalate polystyrene derivative (polyethylene terephthalate -PET-), however, are more easily able to collect moisture in the spaces between the fibers, which is not absorbed by the fibers themselves. These synthetic fibers may be less susceptible to microbial degradation by the nature of the fibers.

This is the reason Shirts (T-shirts) polyester and significantly worse smell a strong odor compared to the same cottons.

There have also been studies showing that some bacteria are best developed in the tissues of a clothes than others: Micrococcus spp. in synthetic clothes; Staphylococcus spp. on both synthetic and cotton; while Corynebacterium spp. in any of them.

Volatile compounds responsible for odor

Volatiles, primarily responsible for the odor, began described in 1991, when the presence of 3-methyl-3-hexenoic acid (3-methyl-2-hexenoic acid) (3M2H), one of the main odor components described axillary. This product is produced by species of Corynebacteria, when degrade secreted components present apocrine glands in the axillary region.

In 2003, a related compound described 3-hydroxy-3-methylhexanoic acid (HMHA), generated from precursors consisting HMHA conjugates and d-glutamine.

Subsequently, they have been involving other compounds, such as sulfur (sulfur), including 3-methyl-3-sulfanilhexan-1-ol (3M3SH). The precursor of this compound has been identified as cysteine conjugate-glycine dipeptide.

Both 3M2H as HMHA occur by cleavage of 3M2H and HMHA-glutamine by the enzyme N-acyl-aminoacylase of Corynebacterium spp. Subsequently it found that Anaerococcus spp., An anaerobic bacteria also cleaves HMHA its conjugated d-glutamine.

Beside the above compounds (3M2H and HMHA) which correspond to volatile fatty acids (VFAs) medium chain (C6-C10), other volatile short-chain fatty acid (C2-C5).

Besides corynebacteria, other bacteria such as Staphylococcus spp skin. contribute to the production of short - chain VFA.

Propionibacterium spp. metabolizes glycerol and lactic acid producing split VFAs as acetic acid and propionic acid.

We have studied many steroids odor producers: 16-androstenes, 5a-androstenol and androsterone-5a;

Diacetyl (2, 3-butanedione) it has been identified as a contributor to unpleasant odor head.


Secretion of apocrine sweat glands contains substances that when metabolized by the bacterial flora Cutaneous aerobic and / or anaerobic generates volatile metabolites that are responsible for the odor of each individual, and unpleasant or offensive odors that may be issued by some individuals. These scents differ depending on various circumstances personal hygiene products that can reduce sweat secretion, or modify the skin flora. Garments can influence these odors, due to the different ability of fibers of different tissues to house components bacteria of the skin flora.